Calculation Method Of Bearing Capacity Research Articles

Experimental and Theoretical Study on the Crack Defect Effect on the Bearing Capacity of a Rectangular Culvert

Rectangular culverts are extensively employed in various municipal projects. Due to their frequent placement in weak strata within urban areas, these structures are susceptible to defects like cracks, which can significantly reduce their bearing capacity and even result in collapse or other failures. This study investigates the mechanical behavior of cracked rectangular culverts through laboratory tests, analyzing both the failure mechanisms and the impact of crack depth on the ultimate bearing capacity (UBC) of the culverts. Focusing solely on the effect of crack depth on the UBC of rectangular culverts with defects, this paper establishes fundamental assumptions and proposes a calculation method for the residual bearing capacity (RBC) of rectangular culverts under crack-induced conditions. The theoretical calculations closely align with the experimental results. The findings indicate that (1) the failure process of a rectangular culvert under trilateral normal external load can be categorized into the initial stage with no visible cracks, the crack progression stage, and the final failure stage; (2) the increase in crack depth leads to a decrease in the UBC of the rectangular culvert, indicating that cracks have a negative impact on its bearing capacity; and (3) when the crack depth reaches the protective layer’s thickness, the UBC of the rectangular culvert reduces by over 30%, providing further evidence that an increase in crack depth significantly diminishes its bearing capacity.

A new semi-empirical bearing capacity calculation method for geocell reinforcement in foundations

This study introduces a novel semi-empirical method that conceptualizes the geocell layer as an additional surcharge and expanding the effective footing width. This method integrates reinforcement mechanisms, including confinement, stress dispersion, and the membrane effects, to calculate the ultimate bearing capacity of foundations reinforced with geocells. An extensive analysis on the angle of load dispersion was conducted, drawing upon numerous studies from the literature and considering various influencing parameters. The proposed calculation method for both drained and undrained conditions was validated using 130 small- and large-scale experimental results. The effectiveness of the proposed method is assessed across different failure modes, soil relative densities, geocell characteristics, load eccentricities, and footing shapes. The study revealed that the calculated bearing capacities generally aligned with the point where the pressure-settlement curve transitions to a steep and relatively straight tangent, which has been identified by various researchers as the ultimate load. Furthermore, existing methods for calculating the bearing capacity of geocell-reinforced soil inadequately capture the pressure-settlement responses, mainly due to differing failure modes between unreinforced and reinforced soils. In contrast, the proposed method, which does not necessitate unreinforced test results, proves effective in determining the ultimate bearing capacity of reinforced soil within acceptable settlement limits.

Seismic behavior of prefabricated lightweight steel composite frame-sandwich wall with enhanced border structure

An innovative prefabricated lightweight steel composite frame-sandwich wall with an enhanced border structure (LSCF-SW), suitable for low-energy consumption low-rise residences, is proposed. Low cyclic loading experiment were conducted to study its seismic behavior. The main parameters include wallboard border type (composite border, mixed border) and steel reinforcement strength (HRB450, HRB500). One full-scale LSCF specimen and four full-scale LSCF-SW specimens are prepared, and their seismic behavior is investigated in terms of failure mode, hysteretic characteristics, ultimate bearing capacity, stiffness degradation, deformation capacity, energy dissipation, and strain characteristics. The results revealed that the sandwich wall (SW) with an enhanced border and lightweight steel composite frame (LSCF) is the primary and secondary seismic fortification lines of the structure, respectively. The LSCF-SW structure exhibited a damage evolution process with four stages. The failure mode involving concrete crushing at the bolted connection area is observed in the specimens with composite bordered sandwich walls (LSCF-SWC), and dense diagonal cracks are discovered in the specimens with mixed bordered sandwich walls (LSCF-SWM). Compared to LSCF-SWC specimens, the ultimate load of LSCF-SWM specimens increases by 23.0 %–50.3 %, and the initial stiffness improves by 16.3 %–42.3 %. The deformation capacity of LSCF-SWC specimens is superior to that of LSCF-SWM specimens. As the steel reinforcement strength increases, the ultimate bearing capacity and initial stiffness of the LSCF-SW also rise. A shear model for the bolt group and a local bending model for the wallboard border are proposed, establishing an ultimate bearing capacity calculation method for LSCF-SW. The calculation results closely align with the experimental results.

Theoretical calculation methods of stable bearing capacity for thin-walled shells with corrosion and variable temperature

AbstractThin-wall shells (steel plates, steel cylindrical shells, steel spherical shells, etc.) are widely used in many engineering fields such as construction, machinery, chemical industry, navigation, and aviation because of their light weight and high strength. Their failure modes under static pressure or impact dynamic load are mostly buckling instability, and the failure is very sudden, often causing structural failure or even catastrophic accidents without obvious symptoms. In this framework, the significance of this paper is that it considers the influence of external environment corrosion on steel shells' bearing capacity using plate and shell classical stability theory, and investigates the stable bearing capacity of thin-wall steel shells in view of corrosion impact. By this approach, a theoretical calculating method for the time-varying stable bearing capacity of plate and shell thin-walled steel members under the simultaneous action of corrosion and temperature changes is obtained, providing a useful theory for complex engineering practices such as corrosion and temperature changes, including fire actions. Noted that for this method with no analytical solution found, its numerical solutions are given in the appendixes.

Axial compressive behavior of steel-hollow core partially encased composite spliced columns

Steel-hollow core partially encased composite spliced frame beam (SHSFB) amalgamates the advantages of steel and composite structures, offering excellent deformation capacity, seismic performance, material savings, and reduced weight. These advantages are also essential for frame columns. Therefore, axial compression tests were conducted on four steel-hollow core partially encased composite spliced columns (SHSCs) and one steel comparison specimen to investigate their failure modes and compressive performance. The test results revealed that the SHSC does not fully utilize the compressive performance of the composite part under compression. Based on these experimental results, improvements were made to the configuration of SHSC, and a new type of SHSC (NSHSC) was further introduced. Finite element parameter analysis was conducted on the hollow-core partially encased composite (HPEC) short columns and NSHSCs, respectively, to investigate the confined effect on concrete in the HPEC section and the influence of different parameters on the compressive performance of NSHSC. The simulated results show that the effectively confined area of concrete in the HPEC section increases with thicker H-shaped steel flanges and narrower stirrup spacing. The compressive performance and failure modes of NSHSC are determined by the lower strength of either the steel part or the composite part. Finally, by integrating concrete confined area division and the compressive stability of variable stiffness column, the calculation method for the axial compressive bearing capacity of NSHSC was proposed. The calculated values exhibit good agreement with the simulation results.

Seismic behavior of lightweight steel frame with thin-walled steel skeleton-lightweight concrete wall

In this study, an innovative prefabricated lightweight steel frame with thin-walled steel skeleton-lightweight concrete composite wall structure (LSF-TSLC) is proposed. The proposed LSF-TSLC has the lightweight steel frame (LSF) as the vertical load-bearing system, whereas the thin-walled steel skeleton-lightweight concrete composite wall (TSLC) acts as the main component for horizontal earthquake resistance. A full-scale LSF specimen and three full-scale LSF-TSLC specimens were prepared considering the variables of wall installation method (embedded, external) and thin-walled steel skeleton distribution (frame type, truss type). The corresponding seismic behavior was experimentally investigated by evaluating the hysteretic characteristics, failure mode, ultimate bearing capacity, deformation performance, stiffness degradation, energy dissipation, and strain characteristics. The results showed that the plastic hinges appeared at the beam ends and column bases of LSF. Due to the shear failure, the embedded and external TSLC exhibited grid cracks and diagonal cracks, respectively. The LSF and TSLC had a good coordinating deformation capacity, while the LSF-TSLC structure had two seismic fortification lines. Compared with LSF, the ultimate bearing capacity and stiffness of LSF-TSLC were increased by 2.1 times and 5.1 times, respectively. The deformation capacity and energy dissipation of LSF-TSLC were significantly improved compared to LSF. The self-tapping nail joint of the embedded wall and the high-strength bolt joint of the external wall had reliable connectivity performance. The numerical simulation of LSF were conducted to verify the plastic analysis model for LSF. And the ultimate bearing capacity calculation method for the LSF-TSLC structure was proposed based on the Strut-and-Tie model.

Research on axial compression performance test and bearing capacity calculation method of newly assembled hollow lattice wallboard

Research on axial compression performance test and bearing capacity calculation method of newly assembled hollow lattice wallboard

Horizontal bearing capacity of post-expanded arm grouting pile foundations

In order to effectively improve the horizontal bearing capacity of pile foundations, this study proposes post-expanded arm grouting technology and associated pile foundations. The horizontal bearing characteristic of the post-expanded arm grouting pile was explored through model tests. The test results indicate that the post-expanded arm grouting pile can increase the contact area between the pile and soil, and can improve the strength of the soil. The horizontal bearing capacity of the post-expanded arm grouting pile was approximately 3 times that of the conventional pile. It also shows that the larger the plate diameter ratio or grouting volume, the higher the horizontal bearing capacity of the post-expanded arm grouting pile. The maximum bending moment of the post-expanded arm grouting pile was located at the pile plate, and the displacement zero point of the new pile was higher than that of the conventional pile. The soil resistance at the pile plate was significantly higher than that of conventional piles, indicating that the pile plate effectively enhances the soil resistance. The improved p-y curve model and horizontal bearing capacity calculation method for the post-expanded arm grouting pile were proposed by considering the pile plate diameter factor. This method was finally verified by experimental results. The results of this study can provide a reference for calculating the horizontal bearing capacity of the post-expanded arm grouting pile.

Axial local bearing behavior of circular reinforced concrete filled steel tube stub columns

In this work, the axial local compression of circular reinforced concrete-filled steel tube (CRCFT) stub columns is studied. Sixteen specimens, including one circular reinforced concrete stub column (CRCC) specimen and fifteen CRCFT specimens, were prepared, considering different variables, such as the local compression area ratio β, sectional steel ratio α, volume stirrup ratio ρv, longitudinal reinforcement ratio ρ, and concrete strength fc. The axial local compression of specimens were experimentally investigated in terms of the damage process, failure mode, load-displacement relationship, ultimate bearing capacity, stiffness, deformation capacity, and strain characteristic. The finite element model of the CRCFT was also developed and validated. The parametric analysis of the local compression area ratio β, sectional steel ratio α, and volume stirrup ratio ρv facilitated the further investigation of the axial local compression behavior of CRCFT. The results showed steel tube buckling and concrete shear failure exhibited by CRCFT specimens. With the increasing local compression area ratio β, the ultimate bearing capacity reduced by 3.6–47.9 %, whereas the local compression strength improvement coefficient βcl increased by 11.8–273.9 %. With the increase in section steel ratio α and volume stirrup ratio ρv, the ultimate bearing capacity, stiffness, and deformation capacity were improved. Longitudinal reinforcement ratio ρ and the concrete strength fc also influenced the stiffness of CRCFT specimens. A simplified calculation method for the ultimate bearing capacity of CRCFT specimens was also presented.

Planar clamping anchorage for CFRP plate: Experimental research, friction-adhesion synergistic mechanism and theoretical model

Carbon fiber-reinforced polymer (CFRP) is an anisotropic material, which poses great challenge to its anchorage. In this paper, the performance of a planar clamping anchorage (PCA) for single-layer CFRP plate cable was investigated through the static tensile test. Influencing parameters included interface treatment form, clamping stress, and anchor length. Two interfacial treatment forms were considered: pure friction and friction-adhesion action. Furthermore, the bearing capacity calculation method of friction-adhesion coupling anchor was developed based on the analysis of the process of adhesion and friction. The results indicate that friction-adhesion coupling action significantly improved the anchor bearing capacity compared to pure friction, and the rate of increase in ultimate load displayed a decreasing trend as the clamping stress increased. Additionally, the error between the theoretical and experimental values of anchor bearing capacity for specimens with friction-adhesion coupling anchor was generally within approximately ±10 %.

Interactive buckling behaviour of Q420–Q960 steel welded thin-walled H-section long column

Considering the broad application prospect of high-strength steel (HSS) in engineering structure, and the limitations present in existing studies on interactive buckling of HSS welded thin-walled box-section long column, both test and finite element analysis were employed to investigate the interactive buckling behavior exhibited by 12 specimens fabricated from Q420–Q960 steels. The detailed analysis considered various aspects, including the failure mode, axial deformation, interaction of local and overall buckling deformation, and the ultimate bearing capacity. Observations revealed that the utilization rate of steel strength diminished with an escalation in both the plate width–thickness ratio and steel strength. An increase in the plate width–thickness ratio correlated with an earlier onset of local buckling, and the influence of steel strength was found to be negligible. More importantly, the limit of the plate width–thickness ratio for columns undergoing interactive buckling increased with a rise in column slenderness and decreased with an increase in steel strength. Taking into account the influence of column slenderness and steel strength, a novel calculation formula for determining the limit of the plate width–thickness ratio was derived. It is noteworthy that Eurocode 3 and JGJ/T 483–2020 were found too conservative for calculating the ultimate bearing capacity, while ANSI/AISC 360–22 was found suitable. Additionally, a calculation method for the ultimate bearing capacity of Q420–Q960 steel welded thin-walled H-section long column was proposed based on the direct strength method.

Compressive bearing capacity of steel dual-angle with cruciform welding filler plates based on failure modes

The bearing capacity of steel dual-angle with cruciform welding filler plates (i.e., DACWP) under axial compression is the primary purpose of this paper. Six DACWP specimens were prepared with different width-thickness ratios (i.e., 15.63, 12.50, 10.42) and slenderness ratios (i.e., 45, 75). Axial compression tests were carried out to analyze the failure mode, load-displacement curve, and load-strain history of the specimens. Subsequently, a finite element model was established and calibrated by test results, providing further insights into the influence of the slenderness ratio and width-thickness ratio on the bearing capacity of DACWP. Finally, a calculation method of bearing capacity based on different failure modes was proposed. The results show that, with a constant width-thickness ratio, the DACWP transits from torsion failure to bending failure with the increase of slenderness ratio. Particularly, the transition slenderness ratio of failure is found to be proportional to the slenderness ratio and the width-thickness ratio. In the case of torsion instability, the slenderness ratio has little effect on the bearing capacity, while the width-thickness ratio exhibits an opposite effect. Specifically, the bearing capacity of DACWP decreases with the increase of slenderness ratio and width-thickness ratio. The calculation formula proposed in this paper can be used to calculate the bearing capacity of DACWP.

Bearing characteristics of mono-column composite bucket foundations for offshore wind turbines in layered soil

The mono-column composite bucket foundation (MCCBF) is a new offshore wind turbine foundation suitable for shallow overburden geology. There are few studies on the bearing capacity and deformation of the new subdivided structure's all-steel MCCBF in layered soil under cyclic loading. This article conducts cyclic bearing characteristics tests on MCCBF in layered soil and shallow overburden layers and studies the ultimate bearing capacity, cumulative rotation angle development rules, and stiffness evolution mechanism. Combined with the finite element analysis results, a calculation method for the ultimate bearing capacity under layered soil is established. The results show that under bidirectional and multidirectional cyclic loading, the ultimate bearing capacity of pure sand changes little, but the strength of clay is reduced, and the ultimate bearing performance decreases. In the clay overlying sand, under high-amplitude cyclic loading, the strength of the sand at the bottom increases, which increases the cumulative angle stiffness and ultimate bearing capacity of the MCCBF. After cyclic loading, the shallow overburden layer will prevent the load from transferring to the deeper soil layer. The foundation will drive the soil in the compartment to slide on the surface of the shallow overburden layer, resulting in a decrease in the load-bearing performance. The initial stiffness of the foundation is increased so that the stiffness change during the cycle is not apparent. Finally, the accuracy of the calculation formula for the ultimate bearing capacity of MCCBF under layered soil is proposed and verified.

Theoretical analysis on the behavior of SPM anchor piles embedded in sand under oblique pullout load with emphasis on the padeye depth

Single-point mooring (SPM) system has been used in offshore engineering for its superiority in overcoming severe sea conditions. However, researches focused on the interaction mechanism between the anchor pile and soil in SPM systems remains insufficient, especially regarding the calculation method for oblique pullout bearing capacity that considers padeye depth. Based on the p-y curve method and load transfer method, this paper presents a simple prediction method for the behavior of anchor piles embedded in sand under oblique pullout load. The theoretical predictions are validated through comparing with results from the three-dimensional finite element method and existing centrifuge model tests. The effect of the loading angle and the padeye depth are analyzed and discussed. A negative bending moment peak and axial force discontinuity phenomenon appear at the padeye depth. The optimal padeye depth for anchor piles in this study ranges from approximately 0.53 to 0.80 times the pile length. When the padeye depth is less than 0.33 times of the pile length, the ultimate bearing capacity of the anchor pile increases with increasing load angles. Conversely, when the padeye depth exceeds 0.33 times the pile length, the ultimate bearing capacity decreases with the increasing load angles.

Method for calculating the bearing capacities of caisson foundations considering the effects of caisson construction

Theoretical analysis of the effects of caisson on the bearing capacities of large caisson foundations was performed, with the slip line simplified as a polyline. Based on the limit balance of forces in active zone, transition zone and passive zone, a simplified bearing capacity algorithm for caisson shaft wall or partition wall with no buried depth and no excavation is established. The effects of caisson excavation on the caisson foundation bearing capacity were examined, and a theoretical formula for estimating the caisson shaft wall or partition wall bearing capacity considering the effects of the angle and depth of excavation was derived. At the same time, the influence of soil weight and the extension of soil slip line from the bottom of the foundation to the surface on the bearing capacity of the foundation is analyzed when there is a certain buried depth between the shaft wall and the partition wall, and a formula for calculating the bearing capacities of buried caisson foundations was proposed. According to the calculation method of caisson shaft wall or partition wall proposed in this paper under the condition of no buried depth and no excavation, combined with the world’s largest north anchor caisson project of Wufengshan Yangtze River Bridge, the plate loading test and inversion analysis are carried out. The results of the test and the simplified calculation method of foundation bearing capacity are in good agreement, and the error of the inversion value and the theoretical calculation value are within 5%. For the theoretical calculation method of foundation bearing capacity considering foundation excavation and buried depth, experiments, inversion analysis or numerical simulation will be carried out to verify the accuracy of the calculation method.

Structural performance of steel reinforced concrete L-shaped columns in high temperature

This paper presented structural performance of steel reinforced concrete (SRC) L-shaped columns under high temperature and axial load coupling effects. Considering the influence of the axial load ratio (0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8), eccentricity (25, 50, 75 and 100 mm), concrete strength (40, 50, 60 and 70 MPa), calculation length (500, 1000, 1500 and 2000 mm), the SRC L-shaped columns were tested and analyzed in high temperature conditions. The results demonstrated that: (1) Concrete surface of all specimens was grayish white with many cracks. With the increasing axial load ratio, the number of cracks decreased and crack width increased. (2) The fire resistance decreased by 1.3–15.1 %, 6.1–14.9 %, and 3.8–7.1 % respectively, with increasing axial load ratio, eccentricity, calculation length; the fire resistance increased by 0.7–5.3 % with increasing concrete strength. (3) Axial displacement trend first increased gradually because of the thermal expansion of concrete, and decreased gradually after reaching the maximum axial expansion deformation. With increasing axial load ratio, the maximum axial expansion deformation decreased by 42.4–60.2 %, the time of displacement to reach the maximum expansion deformation decreased by 29.7–57.0 %, and the time of displacement to reach 0 mm decreased by 272.7–366.2 %. Finally, the calculation method for displacement and maximum bearing capacity in high temperature was proposed according to principle of virtual work, which served as a guide for fire evaluation of SRC L-shaped columns.

Stiffness and ultimate strength of multi-ring-stiffened tube-gusset X-joints with dual-function stiffeners

Tube-gusset (TG) joints that use stiffener plates as connecting plates for the crossarm chord are the main method for joining chords to tower bodies of transmission steel pipe towers. These joints experience the highest compression loads of the entire transmission tower structure. This study presents experimental research, numerical simulations, and theoretical analysis on the TG joint with a five-ring stiffener, where the middle stiffener plate serves as a connecting plate (referred to as C-Stiffener). This study elucidates the failure mechanism and mechanical characteristics of the C-Stiffener, identifies the key factors influencing its local buckling under compression, and proposes a stiffness calculation method for this type of stiffener plate. A calculation approach for the ultimate bearing capacity of the C-Stiffener is established by utilising its stiffness-deformation curve and a calculation method for the ultimate bearing capacity of the five-ring-stiffened TG joint under axial compression loading is proposed. The findings of this study can provide guidance for the meticulous design of joints between the crossarms and bodies of steel pipe transmission towers, thereby ensuring the safety and stability of transmission lines.

Flexural Performance of Reinforced Concrete Beams Strengthened with a Novel High-Strength and High-Toughness Epoxy Mortar Thin Layer

The flexural performance of RC beams strengthened with a novel high-strength and high-toughness epoxy mortar thin layer was investigated through four-point flexural tests on two contrast beams and two strengthened beams. The effects of this strengthening method on the failure modes, crack distribution, load–deflection curves, and bearing capacity of the RC beams with two reinforcement ratios were studied. The experimental results revealed that the contrast beams exhibited the typical bending failure modes where the failure mode of the reinforced beam is the yielding of the tensile reinforcement of the original beam and then fracture damage of the new epoxy mortar-reinforced thin layer. No debonding phenomenon was observed between the reinforced thin layer and the original concrete, and no visible cracks appeared before the tensile failure occurred in the thin layer. The cracks in the reinforced beams developed slowly, increased in number, and decreased significantly in width and spacing. The stiffness of the strengthened beam increased significantly, while its deformation ductility coefficient noticeably decreased. Compared to the corresponding contrast beams, the cracking load for strengthened beams A1 and B1 increased by 14% and 23%, respectively; the yield load increased by 32% and 40%, respectively; and the peak load increased by 18% and 17%, respectively. Finally, a calculation method for the flexural bearing capacity of RC beams strengthened with the novel epoxy mortar thin layer based on the flat section assumption was proposed. The calculated values showed a good agreement with the experimental values (with errors at −11.73% and 4.14%, respectively), providing a valuable reference for further research and application related to this kind of reinforcement method.

Study on mechanical properties and bearing capacity calculation of eccentric compression of RC columns reinforced with prestressed lattice steel

The external steel structure and RC column under eccentric compression have a reduced ability to work together, and using prestressing technology can significantly improve their ability to work together. Therefore, the paper proposes a new prestressed column reinforcement technology by adopting a space profile steel structure instead of angle steel and combining prestressing technology with the bolted connection. By conducting eccentric compression test studies on 11 specimens with different reinforcement methods, prestressing and eccentricity, load-displacement curves, stress distribution laws, ultimate bearing capacity, damage modes and prestressing influence rules were obtained. The main conclusions are as follows: prestressing can significantly improve the ability of external reinforcement steel structure and core column to work together and inhibit the development of concrete cracks. Compared with the traditional angle steel reinforcement, the bearing capacity is increased by 17.5 %, the stiffness is increased by 26.6 %, and the ductility is increased by 12.3 %. However, the reinforcement effect will be reduced if the prestressing is too large. It is recommended that the prestressing should be applied according to the size of 0.09 fc of the unilateral area of the core column. According to the prestressed lattice steel constraint mechanism, a mechanical analysis model of the reinforced member was established. Finally, based on the cross-section equilibrium method, a calculation method of eccentric compressive ultimate bearing capacity was proposed, and the research results can provide a basis for the engineering application of the new reinforcement method.

Behaviour of concrete-filled circular steel tubular K-joints in wind turbine towers

The advantages of concrete-filled steel tubular lattice towers in stress efficiency, material consumption, and industrial construction are significant for the future development of ultra-long blades, ultra-high towers, and large-capacity units. The stress state of the joints is a key component of a wind tower structure. Therefore, experiments were conducted on four concrete-filled circular steel tubular (CFCST) K-joints in a lattice wind turbine tower, along with one hollow circular steel tubular (HCST) K-joint for comparison. The test results revealed that the CFCST K-joints failed due to local and overall buckling of the compression web, whereas no plastic deformation occurred on the chord. The stiffness of the CFCST K-joints significantly improved, and the stress concentration around the intersecting line was significantly reduced. Existing structural codes, both domestic and international, underestimate the bearing capacity of CFCST K-joints because the contribution of the core concrete cannot be accounted for. Finite element analyses indicate that the bearing capacity of the CFCST K-joints is dependent on the failure mode, primarily influenced by the thickness ratio τ and the angle θ. To prevent joint failure in the CFCST lattice wind turbine towers, specifically suggest τ ≤ 1 and θ ≤ 45°. Based on the bearing capacity calculation method proposed by CIDECT for HCST K-joints, design equations were obtained to predict the punching shear bearing capacity of CFCST K-joints using the least-squares method. The established formula exhibited high accuracy through regression verification.